1. Field of the Invention
The present invention relates to an optical encoder.
2. Description of Related Art
A typically known optical encoder includes: a scale having latticed scale markings; a detecting head having a light-emitting element that emits light onto the scale and a light-receiving element that receives the light emitted by the light-emitting element to be reflected or transmitted by the scale; and a connector connected to the detecting head via a cable. The optical encoder measures the position of the detecting head relative to the scale based on the light received by the light-receiving element (see, for instance, Patent Literature 1: JP-A-2006-3307).
The optical encoder disclosed in the Patent Literature 1 includes a scale base (scale), a detector head (detecting head) and an output connector (connector) and measures the position of the detecting head relative to the scale.
When the optical encoder is used, a user attaches the scale and the detecting head respectively to two objects to be measured that are relatively displaceable. At this time, the scale and the detecting head have to be attached in an appropriate positional relationship so that the light emitted from the light-emitting element is reflected or transmitted by the scale and received by the light-receiving element and the intensity of the light received by the light-receiving element comes within a predetermined range.
Specifically, an optical encoder disclosed in Patent Literature 2 (JP-A-05-133732) includes an LED (Light Emitting Diode) provided on a read head, the LED changing emission color thereof based on an electric signal outputted by a light-receiving element in accordance with a distance (positional relationship) between a scale and the read head. A user can adjust the positional relationship between the scale and the read head by visually checking the emission color of the LED while moving the read head relative to the scale.
However, according to the optical encoder disclosed in the Patent Literature 2, since the user has to visually check the emission color of the LED while moving the read head relative to the scale, the positional relationship between the scale and the detecting head cannot be easily adjusted. Further, depending on the attachment position of the read head onto the object, it is difficult for the user to visually check the emission color of the LED, so that the positional relationship between the scale and the detecting head cannot be easily adjusted.